22 DIVISION I. — GENERAL MORPHOLOGY. 



membranes, which our present knowledge enables us to add to what has been already 

 said, is that they only occur in Fungi with septate hyphae ; the structure of the 

 mycelium varies of course in particular points in each spec; 



Special generic and specific names have in former times been repeatedly given 

 to mycelial membranes which are only known in the sterile state. Persoon's genus 

 Mycoderma 1 may be composed to a great extent of forms of this kind which belong 

 to the Hyphomycetes or to the Ascomycetes. Racodium cellare of Persoon 2 which 

 forms the well-known olive-brown coating on old casks in cellars is, as far as we 

 know, a mycelium formed of loosely interwoven filaments, the origin and reproductive 

 organs of which are still quite unknown. 



The mycelial membranes named by Tode and Persoon Athelia and Xylostroma 

 are of a firmer kind. The Athelieae are the sterile states of the Thelephoreae 

 (Thelephora, Hypochnus), in part perhaps their undeveloped sporophores ; the Xylo- 

 stromeae, which occur as broad flat formations of a woody or leathery texture in the 

 decaying stems of trees, are the like states of firm wood-destroying Hymenomycetes, 

 such as Polyporus abietinus, Thelephora hirsuta, Th. crocea, Schrad., Th. seiigera, 

 Fr., Th. suaveolens, Trametes Pini, Daedalea quercina, and other species of these and 

 allied genera. 



Section VII. The hyphae of the mycelia of many Fungi unite together into 

 strands, which in their form, branching, and mode of spreading in the substratum 

 look to the unassisted eye more or less like the roots of higher plants. Even 

 some species of Hyphomycetes, those for instance known as Acrostalagmus, show 

 a tendency to this kind of formation. But it is most frequent among the Fungi 

 which have compound sporophores, such as the Phalloideae, many Lycoperdaceae, 

 the Hymenogastreae, Nidularieae, and Sphaerobolus, in many of the Agaricineae, 

 as A. campestris, A. praecox, A. dryophilus, A. aeruginosus, A. metatus, A. andro- 

 saceus, A. Rotula, A. platyphyllus and A. melleus, and amongst Ascomycetes, such 

 as Elaphomyces, some species of Genea, Peziza Rapulum, Bull., and P. fulgens ; 

 the endophytic mycelium of Polystigma stellare, Lk., may be added to the list. Ii is 

 evident from these examples that the formation of strands is not necessarily found in 

 all the spe< ies that belong to the cycles of affinity indicated by the above names; on 

 the contrary it may be wanting in one of two nearly allied species and be found in the 

 other. 



The strands, as has been said, spread themselves out in and on the substratum, 

 growing at the apex and putting out similar branches, the arrangement of which 

 scarcely follows any exact rule even in the same species. In each case the strands 

 may either be in part Ucc and tapering, or they may in part unite to form a coarser 

 or finer net-work, or they may in part lose themselves in a loose filamentous web, or 

 a single strand or several combined may expand into membranes, which spread 

 over the substratum or spin themselves round bodies contained in it. Fresh 

 strands may then take their rise from these expansions. This variation of form is 

 essentially dependent on the character of the environment and its influence on 

 the nutrition of the Fungus, as is well shown in the case of Agaricus melleus to be 

 hereafter described. 



In most cases which have been examined the strands are composed of uniform 



' Mycol. Eurof. p. 96. Syn. Fungor. 701. 



